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PSB C04 RF system Consolidation or upgrade?
M. Paoluzzi – CERN BE-RF
04/21/23 1
C02 : 4 cavities in 2 straight sectionsfreq= 0.6-1.8 MHz
Vgap=8 kVRs≈350Ω seen by the beam
C04 : 4 cavities in 1 straight sectionfreq 1.2 3.6 MHz
Vgap=8 kVRs≈350Ω seen by the beam
C16 : 4 cavities in 1 straight section freq 6.0- 16 MHz
Vgap=6 kVRs≈2 kΩ seen by the beam
04/21/23 2
Consolidation foreseen C02, C16
• Replacement of ITL, power supplies, cables
(rebuilt the systems keeping the cavities and amplifiers)
• Possibly move AVC and Tuning loops to Low Level
Consolidation foreseen C04
• Same as above but power stage replacement
(improve mean available power and current for beam
loading compensation)
Is it the time to envisage a technology change?
04/21/23 3
Narrow band
Tuned systems
Highly optimized
Almost no room for Vgap increase
Further reduction of Rs very difficult
04/21/23 4
Finemet LEIR Cavity
A single cavity covers the range 0.35÷5 MHz
Cavity length 0.5 m
Gap voltage 4 kV (tested at 5 kV)
No tuning
AVC integrated in Low Level
But…
… diameter incompatible with PSB overlapped rings
04/21/23 5
Finemet in PSB
Maximum outer diameter OD=330mm
Inner diameter ID=200mm
Standard Finemet thickness 25mm
Two kind of material:
• Standard LEIR like : FT3M (data available from small rings)
• New low loss : FT3L (Thanks to KEK and Chihiro Ohmori for providing data)
04/21/23 6
Air cooling test on small rings (OD=133mm) :
- Simple blower on each ring side
- With 500kW/m3 t MAX≈70°C
- Maximum inside temperature unknown
- Limit temperature
- Suggested from Hitachi t MAX≤100°C
- KEK booster experience t MAX≈100°C
- J-PARC experience t MAX≈200°C for few hours
04/21/23 7
Minimum peak voltage 380V for FT3L300V for FT3M
@ 1 MHz
Note:f Injection ≈1 MHz with LINAC4
One C04 cavity contains 50 rings
In the range 1÷4 MHz : VGAP=15÷17 kV with FT3MVGAP=19÷29 kV with FT3L
04/21/23 8
Basically working on a capacitor
Almost no difference with increased
number of rings
04/21/23 9
Alternative approach based: use two rings (FT3L) and 1 gap
Each ring can accept 500pF and still cover the 1÷4 MHz
band . RPmin is ≈100 Ω (per ring)P≈1500W for 700V across two rings
This can be supplied by a solid-state amplifier(in PSB solid state amps used since 1987!!!)
V A C U U M C H A M B E R
G A P
A I R O U T
1 0 - 1 5 C M
F I N E M E T
A I R I N
04/21/23 10
Beam current
04/21/23
ejAFTT
ejI
T
eBunchCh
Tdt
d
d
dQ
dt
dQI
eBunchCheBunchCh
ddeBunchCh
peakRFRFRF
LRFRF
L
L
L
L
L
LL
@7.22101377.0
102.3
180138
102106.1@ˆ
arg2ˆmaxmaxˆ
arg2
cos
argˆ
sinˆ)(arg
6613192
2
0
00
w/o acceleration, the h1 bunch length:φL 138o (2.4 rad or 220 nsh1 @ej.)Total charges per bunch= 2 E13h1
(sinus shape approx.)
For a pure h1 or h2 beam,the beam peak current is 22.7 A @ ej
1st rf harmonic : ÎH1 = 9.56 A2nd rf harmonic: ÎH2 = 6.06 A
φL , TL
I
Sine shape approximation
11
Slide provided by A. Blas CERN BE-RF
MRF157 Mosfet600W up to 80MHz
To provide 800W(2 units push-pull)
ID-peak≈32AID-DC≈10A
04/21/23 12
MRF151 Mosfet150W to 175MHz
To provide 200W(2 units push-pull)
ID-peak≈12AID-DC≈4A
• Shunt resistance of each gap Rs≈200 Ω• To get the present 8kV need 12 gaps• Total impedance seen by the beam Rstot≈2400 Ω• Impedance of present cavities (including FB) ≈350 Ω
• We must reduce Rstot and compensate beam loading with:
• ≈20 dB RF feedback seems possible with 10 ns delay in the loop.
•1 turn feedback: difficult (nevertheless possible) because revolution time is only ≈500 ns at extraction.•Combination of both
04/21/23 13
The cavity could be used as combiner for push-pull operation and driven by 2 amplifiers similar to the LEIR 1kW drivers.
The total power could easily be brought to 2 x 2 kW simply increasing the DC supply by 15%.
The 120W (200W) power module delay is 12 ns and the 9 ways combiner 4ns. Both could be reduced and 10 ns total seems within reach.
04/21/23 14
04/21/23 15
Simulated system response:1 Finemet ring driven by 9 combined 200W modules
and feedback including delay .
Amplification chain response.
200W module.
1 ring impedance.
Advantages
• Modular system.•Reduced machine space and/or increased installed voltage.• Possibility of installing spare cavities as hot back-up.• No tuning loop.• Simplified solid-state system.
Risks• Additional new system at restart with LINAC4.• New technology and configuration.• Complete new design.
04/21/23 16
How could we proceed…• 2010-2011 Design and produce a first section.… if successful then:•2012 produce and install and test a full set of cavities for the required 8 kV.
They should fit in the place of one of the present C04 cavities. •2013 Tests with beam (1 ring and C02 system still in place)… if successful then:•2014-2015 Proceed with full scale construction and
C02/C16 renovation•2016 Installation
… but for security•2011 Design a first C04 improved RF power amplifier.•2012 Produce and install C04 improved RF power amplifier.•2013 Tests with beam (1 ring)•2014-2015 Depending on 2013 tests start C02/C04/C16 renovation or
stop C04 renovation it and proceed with new system.•2016 Installation
04/21/23 17